Method for establishment of connections of pre-determined performance for a packet-oriented communication network with a resource manager

ABSTRACT

The invention relates to the control of transmission resources in individual transmission paths in a packet-oriented communication network, whereby data-packet address information (A 1,  A 2 ) which identifies the origin and the goal of the data packets (DP 1,  DP 2 ), is transmitted to a resource manager (RM), responsible for a transmission path (US), from a network transmission device (R 1,  R 2 ). On a resource request (RA), for a connection to be subsequently generated, the origin and goal thereof are compared with the origin and goal of the previously transmitted data packets (DP 1,  DP 2 ) by the resource manager (RM). Should there be agreement, the resource manager (RM) can deduce that the connection to be established can equally run over the corresponding transmission path (US). Correspondingly, establishment of further connections occurs, depending upon the available resources of said transmission path (US).

[0001] In many packet-oriented communication networks, such as theInternet, no performance is guaranteed for connections between terminalsin these communication networks if no additional precautions are taken.The performance of a connection is also frequently known as “Quality ofService” (QoS) and can include different transmission and connectionresources, such as the transmission bandwidth, the transmission rate,the permissible error rate and/or the transmission duration.

[0002] In up-to-date communication systems, which are frequently basedon such packet-oriented communication networks, resource managers areprovided in order to ensure a predetermined performance. In each casethese are assigned to a communication network or subnetwork in order tomanage its transmission resources. When there is a resource manager,transmission resources which can be predetermined specifically forconnections can be reserved for the connections which have to beestablished. Following a successful reservation of transmissionresources, the resource manager monitors the continuous availability ofthe reserved transmission resources for the connection concerned.

[0003] Usually when a connection needs to be established, its origin anddestination are transmitted to a resource manager so that it can reservethe necessary transmission resources. The resource manager then uses thetransmitted origin and destination information to determine the pathover which the connection needing to be established will run. To do thisaccording to known prior art, the resource manager needs preciseinformation about the complete topology of the communication network.This information is transmitted to the resource manager very expensivelywith the aid of a routing protocol. A method of this kind is describedin the document “Performance of QoS Agents for Provisioning NetworkResources” by Schelén et al. in the Proceedings of IFIP SeventhInternational Workshop on Quality of Service (IWQoS'99), London, June1999.

[0004] In many cases connections need to be established betweendifferent subnetworks in a communication system, for which purpose thesubnetworks themselves may well have a very large transmissionbandwidth, but are coupled over a transmission path with aproportionately narrow transmission bandwidth. A typical example of thisis when local area networks (LANs) are coupled over a public telephonenetwork. In this case the telephone network with its proportionatelynarrow transmission bandwidth represents a bottleneck for data needingto be exchanged between the local area networks. This leads to theproblem of how to control transmission resources efficiently even forconnections running through such bottlenecks.

[0005] The object of the present invention is to specify a method for apacket-oriented communication network, for the purpose of establishingconnections of predetermined performance, a method which enablestransmission resources for connections running over individualtransmission paths, in particular individual transmission bottlenecks,to be efficiently controlled at low cost.

[0006] This object is achieved in that there is a method with thefeatures of Claim 1.

[0007] Within the scope of the method according to the invention, atransmission resource in a transmission path is managed by a resourcemanager. A network transmission device which transmits data packets overthe transmission path transmits to this resource manager data packetaddress information identifying the origin and destination of the datapackets. The resource manager thus has the information that data packetswith the corresponding origin and destination will be transmitted overthe transmission path concerned. On a subsequent resource request for aconnection to be established, if the origin and destination thereofmatch the origin and destination of the previously transmitted datapackets, the resource manager can then deduce that the connection to beestablished will—at least with a very high probability—likewise berouted over the corresponding transmission path. Correspondingly,further connections are established, depending upon the availableresources of the said transmission path.

[0008] An advantage of this method consists in that with the packetaddress information, current information on the path of data packets orconnections is transmitted to the resource manager, in which aninformation database is then automatically updated via the connectionrouting management in the communication network. This is particularlyadvantageous in those communication networks where the routingmanagement of a path or connection between predetermined terminalschanges frequently.

[0009] With regard to the method according to the invention, let it beunderstood that a connection also includes subelements known as virtualconnections, connection line groups, connection paths or general datastreams, with a defined origin and destination in each case. In thissense devices such as terminals, network nodes, switching equipment,communication networks, partial networks or subnetworks can beconsidered as the origin and destination of such connections.

[0010] The performance of a connection under the control of the resourcemanager can involve quite different transmission resources, such astransmission bandwidth, transmission rate, permissible error rate,transmission delay and/or any other Quality-of-Service parameters, asthese are known, and may if necessary be specific to particular serviceclasses or priority classes.

[0011] Advantageous embodiments and developments of the invention aredescribed in the dependent claims.

[0012] Link information can advantageously be transmitted to theresource manager with the data packet address information, enabling theresource manager to identify the transmission path concerned. Typicallink information can consist of data identifying the networktransmission device and if necessary data identifying one of themultiplicity of transmission paths connected thereto. By thetransmission of link information, the resource manager is put in aposition to exercise separate control over a multiplicity oftransmission paths, each of which is identifiable with the aid of thelink information, by means of the method to which the invention relates.

[0013] In an advantageous development of the invention the networktransmission device can—if necessary at regular intervals—transmitinformation to the resource manager about the available set of resourceson the transmission path. In this way the extent of the resources beingmanaged by the resource manager can be updated on the basis of thelatest transmission situation. This is particularly advantageous in thatit directly notifies the resource manager about unforeseen adverseeffects on the behavior of the transmission path, without needing tomake a detour through a costly routing protocol.

[0014] In addition various measures can be taken to reduce the amount ofdata to be transmitted from the network transmission nodes to theresource manager:

[0015] For example, before transmitting data packet address informationa check is first made on whether data packet address information withthe same contents has already been sent earlier. Transmission then takesplace only if the check turns out to be negative. In order for the checkto be possible, previously sent items of data packet address informationmust be stored by the network transmission device.

[0016] Furthermore, depending on the data packet address information,the network transmission device can send the resource manager routinginformation for recognizing connections running over the transmissionpath. Such routing information can typically be determined by accessinga routing table. In this instance routing information can mean, forexample, that all data packets with an origin and/or destinationsubnetwork address specified in the routing information will betransmitted over the transmission path.

[0017] In addition the data packet address information in a data packetcan be transmitted dependent on transmission information contained inthat data packet. By this means it is possible for instance for datapackets that are exchanged between non-connectable terminals orapplications on the communication network to be excluded from using themethod to which the invention relates. Such packets can be recognized bythe network transmission nodes by means of transmission informationcontained in the data packet, such as an origin address and/ordestination address, or in certain cases a protocol number and/or portnumber.

[0018] An exemplary embodiment of the invention will be explained ingreater detail below with the aid of the drawing.

[0019] This illustrates the following in diagram form:

[0020]FIG. 1 shows a communication system with two subnetworks connectedover a transmission path in the course of transmitting data packets and

[0021]FIG. 2 shows the same communication system in the course ofestablishing a connection.

[0022]FIG. 1 and FIG. 2 show in each case diagrams of the samecommunication system with two packet-oriented, preferably Internetprotocol based communication subnetworks LAN1 and LAN2, which in thisexemplary embodiment take the form of local area networks. Local areanetwork LAN1 has a router device R1 which is connected over atransmission path US to a router device R2 on local area network LAN2.For the exemplary embodiment it can be assumed that the transmissionpath US has significantly fewer transmission resources than the localarea networks LAN1 and LAN2 and therefore represents a transmissionbottleneck for a data exchange between local area networks LAN1 andLAN2. A situation of this kind frequently occurs in practice, forinstance when a multiplicity of local area networks belonging to acompany are located in different places and connected over the publiccommunication network or the Internet. Local area networks connectedtogether in this way are also frequently known as a “virtual privatenetwork” (VPN).

[0023] Instead of the router devices R1 and R2, which here take the formof devices known as edge routers, it is also possible to connecttogether the local area networks LAN1 and LAN2 with the aid of elementsknown as gateways, switching devices, modems or general network nodes ornetwork transmission nodes belonging to a private or publiccommunication network.

[0024] To manage the transmission resources of the local area networksLAN1 and LAN2 and in particular the transmission path US, a centralresource manager RM is arranged within the communication system. Theresource manager RM is the element in the communication system that isresponsible for reserving transmission resources for connections whichneed to be established, and for ensuring the performance of establishedconnections. Transmission resources or performance can involve quitedifferent transmission parameters, such as a maximum or mediumtransmission bandwidth, transmission delay and/or transmission errorrate. For all connections which require a performance guarantee in thecommunication system, the corresponding transmission resources must berequested from the resource manager RM and released again once theconnection is cleared.

[0025] In addition a terminal EG1 is connected to local area networkLAN1 and a terminal EG2 is connected to local area network LAN2.Terminals EG1 and EG2 can take the form of any terminal for thecommunication of speech, video and/or data, or can even be a personalcomputer. Address information A1 is assigned to terminal EG1 and addressinformation A2 is assigned to terminal EG2. Terminals EG1 and EG2 can beuniquely addressed and identified in the communication system by addressinformation A1 and A2. In an alternative embodiment of the invention itis possible to provide another router device or switching device oranother communication system network node in place of at least one ofthe terminals EG1 and EG2.

[0026] Furthermore the communication system has a central device knownas a gatekeeper GK which is connected to the resource manager RM. Thegatekeeper GK is responsible for logical control, that is, theestablishment, clearing down and monitoring of connections in thecommunication system. To establish a connection with guaranteedperformance, the origin and destination of the connection to beestablished must be sent to the gatekeeper GK together with a resourcerequest. In the exemplary embodiment the gatekeeper GK satisfies ITU-Tstandard H.323.

[0027] According to another embodiment a device known as an SIP server,which supports the protocol known as SIP (session initiation protocol)in accordance with the IETF standard, can be used instead of thegatekeeper GK.

[0028] The resource manager RM moreover has an allocation table TABwhere the origin and destination addresses of data transfers in thecommunication system are assigned to individual transmission paths.

[0029]FIG. 1 shows the communication system in the course oftransmitting data packets DP1 and DP2 over transmission path US. In theexemplary embodiment, data packets DP1 are transmitted into local areanetwork LAN1 by terminal EG1, in the scope of a data transfer which isnot further defined, with address information A1 as the origin addressand address information A2 identifying terminal EG2 as the destinationaddress. The router device R1 of local area network LAN1 recognizes bymeans of the destination address A2 that the destination terminal EG2 isaccessible over local area network LAN2 and consequently transmits datapackets DP1 over the transmission path US and the router device R2 intolocal area network LAN2. This then forwards data packets DP1 to thedestination terminal EG2. In a similar way data packets DP2 aretransmitted into local area network LAN2 by terminal EG2, in the scopeof another data transfer which is not further defined, with addressinformation A2 as the origin address and address information A1identifying terminal EG1 as the destination address, and are transmittedfrom there over local area network LAN1 to destination terminal EG1.

[0030] In the exemplary embodiment, both the data transfer from terminalEG1 to terminal EG2 and the data transfer in the opposite direction arecarried out over the transmission path US. In general, however, the pathtaken by data transfers can also be dependent on the direction oftransfer. Furthermore the transmission resources of the transmissionpath US can be different for the two directions of transmission, andaccordingly the resource manager RM generally manages them separately.

[0031] In relation to the invention the router device R1 transmits theorigin address contained in the data packet DP1 which is to betransmitted, in this example A1, and the destination address, in thisexample A2, together with link information LUS identifying thetransmission path US, to the resource manager RM. The resource managerthen stores the address information A1 as the origin address, theaddress information A2 as the destination address, and the linkinformation LUS, cross-allocated, in the allocation table TAB. In asimilar way the router device R2 transmits the origin address containedin the data packets DP2 which is to be transmitted, in this example A2,and the destination address, in this example A1, together with linkinformation LUS identifying the transmission path US, to the resourcemanager RM. The resource manager stores the address information A2 asthe origin address, the address information A1 as the destinationaddress, and the link information LUS, cross-allocated, in theallocation table TAB. The resource manager RM can therefore determine byaccessing the allocation table TAB that both a data transfer fromterminal EG1 to terminal EG2 and a data transfer in the oppositedirection are each being carried out over transmission path US. Readingand transmitting the address information A1 or A2 contained in the datapackets DP1 or DP2 can be carried out by the router devices R1 and R2preferably with the aid of an element which additionally has to beimplemented, known as a monitoring component, for observing data packettraffic. The transmission of information from the router devices R1 andR2 to the resource manager RM preferably takes place over logicalsignaling channels.

[0032] Preferably the router devices R1 and R2 only ever transmitaddress information and link information to the resource manager RM whenthe information concerned changes. For this purpose address informationto be transmitted from the router devices R1 and R2 to the resourcemanager RM is stored and compared with the current address informationcontained in subsequent data packets. The current address information isonly transmitted to the resource manager RM if it does not match thestored address information. This prevents identical address and linkinformation for each of the individual data packets DP1 or DP2 beingrepeatedly transmitted to the resource manager RM.

[0033] The amount of information to be transmitted from the routerdevices R1 and R2 to the resource manager RM can also be reduced bysending the resource manager generalized routing or address information,for instance in the form of subnetwork addresses. The router devices R1and R2 can frequently recognize with the aid of a data packet that hasto be sent over the transmission path US, that yet more data trafficwill be carried over the transmission path US. In this case the routerdevice R1, for example, by accessing a routing table which states thatall data packets directed to the local area network LAN2 are to betransmitted over the transmission path US, can determine with the aid ofa data packet arriving from terminal EG1 that all data packets fromterminal EG1 which are to be transmitted into local area network LAN2,regardless of the destination terminal, will be sent over thetransmission path US. In this case the router device R1 can send theresource manager RM the address information A1 as the origin address andthe subnetwork address of the local area network LAN2 as the destinationaddress.

[0034]FIG. 2 shows a diagram of the communication system establishing aconnection from terminal EG1 to terminal EG2. The connection to beestablished is independent of the preceding data transfers between theterminals EG1 and EG2. A situation of this kind frequently occurs when,for example, terminals EG1 and EG2 are in the form of personal computersbetween which both an active transfer of files takes place without aperformance guarantee and connections for transmitting voice overInternet protocol (VoIP) are established with guaranteed performance.

[0035] Within the scope of establishing a connection, connectionsignaling VAS is carried out between the terminal EG1 and the gatekeeperGK as well as between the gatekeeper GK and the terminal EG2. For thispurpose logical signaling channels are provided between the terminal EG1and the gatekeeper GK as well as between the gatekeeper GK and theterminal EG2. The logical signaling channels for connectionestablishment signaling are shown in FIG. 2 by unbroken double-headedarrows. Connection establishment signaling is preferably carried out inaccordance with ITU-T Recommendation H.323v2. This type of connectionestablishment signaling is also frequently known as “fast connect”.

[0036] Within the scope of connection establishment signaling VAS, theaddress information A1 identifying the connection origin EG1, theaddress information A2 identifying the connection destination EG2 and aresource request RA are transmitted to the gatekeeper GK by the terminalEG1 initiating the connection. The gatekeeper transmits the resourcerequest RA and the address information A1 and A2 to the resource managerRM and initiates the connection between the terminals EG1 and EG2.

[0037] According to an alternative embodiment of the connectionestablishment, the terminal EG1 can transmit to the gatekeeper GK alogical destination address (not shown) which identifies the connectiondestination EG2, such as an alias address, e-mail address, URL (uniformresource locator) or E.164 address. The logical destination address isthen converted by the gatekeeper GK into a transport address identifyingthe connection destination EG2, in this example A2, and transmitted inthis form to the resource manager RM. The transport address in this caserefers to the address information by which the data packets can besteered through the communication system. A transport address of thiskind can, for instance, be composed of an IP address (IP: Internetprotocol) and a port number.

[0038] When the address information A1 and A2 is transmitted, the originand destination of the connection that needs to be established is knownto the resource manager RM, but not its path.

[0039] In order to obtain information on the path of the connection thatneeds to be established, the resource manager RM looks in the allocationtable TAB for an entry with an origin address that matches the addressinformation A1 transmitted by the gatekeeper GK and a destinationaddress that matches the address information A2 transmitted by thegatekeeper GK. If a subnetwork address is contained in the allocationtable TAB as the origin address or destination address, a match betweenthis subnetwork address and the corresponding subnetwork address part ofthe address information A1 or A2 concerned transmitted by the gatekeeperGK is judged to be a match within the meaning of the method to which theinvention relates.

[0040] In the exemplary embodiment the very first entry in the table isfound to be in agreement and the link information LUG for this entry isread. By means of the link information LUG read in this way, theresource manager RM recognizes that the connection which needs to beestablished will be routed over the transmission path US identified bythe link information LUG. This causes the resource manager RM to takeinto consideration in particular the currently available transmissionresources of the identified transmission path US when makingtransmission resources available in accordance with the resource requestRA.

[0041] If the requested transmission resources on the transmission pathUS are not currently available, establishment of the connection iscancelled. In the event that no entry showing agreement in the abovesense is found in the allocation table TAB, the connection establishmentmay preferably be continued, although the resource manager RM does notknow that the connection is routed over the transmission path US. Thismethod can in some cases lead to a situation where the requestedtransmission resources can no longer be guaranteed after the connectionis established. Such cases are very rare however, since in the main theycan occur only during a short starting phase of the communication systemwhen terminals EG1 and EG2 have not yet exchanged any data packets. Evenso, in order to avoid such cases, reserves of resources can be providedby the resource manager RM.

[0042] Once the connection is established, useful data DATA can beexchanged between terminals EG1 and EG2 over the local area networksLAN1 and LAN2 and the transmission path US with guaranteed performance.

[0043] As already mentioned above, the transmission resources availableon the transmission path US are considerably less than the transmissionresources of the local area networks LAN1 and LAN2. For this reason thetransmission resources available on the transmission path US are thecritical factor for the control of the transmission resources for theconnection. The special control of the transmission resources on thetransmission path US by the resource manager RM is indicated in FIG. 2by a dotted arrow.

[0044] The transmission resources on the transmission path US can ifnecessary be managed and controlled by service class, priority classand/or transmission direction. A simple implementation of such aresource management consists in dividing the data traffic into differentservice and/or priority classes and assigning to each of these classes aproportion of the available transmission resources of transmission pathUS—if necessary making them specific to the direction of transmission.These kinds of data traffic classes are also frequently referred to asDiffServ classes. Preferably a class of data traffic for connectionlessdata traffic, i.e. traffic for which no logging on is required, can alsobe provided. Data traffic belonging to this class of traffic would haveno performance guarantee. To manage traffic classes the resource managerRM can be provided with a resource table (not shown), with entries foreach individual traffic class showing the transmission resourcesreserved for connections and the resources still remaining.

[0045] So that data packets that have to be transmitted can be allocatedto individual traffic classes with guaranteed performance, these datapackets can be labeled with traffic class information. From thislabeling the router devices R1 and R2 can recognize the traffic class towhich a data packet due for transmission is assigned, and whichtransmission resources are reserved for this data packet if appropriate.

[0046] It is furthermore possible to provide for the resource manager RMto notify the router device R1 or R2 about every successful resourcereservation affecting the transmission path US. The router device R1 orR2 can then be operated in such a way that only data packets fromconnections for which the resource reservation has been notified in thisway will be handled in accordance with the resource reservation andtraffic class association concerned.

1) Method for a packet-oriented communication network for theestablishment of connections of predetermined performance using anetwork transmission device (R1, R2) and a transmission path (US), inwhich a) a transmission-oriented set of resources on the transmissionpath (US) is managed by a resource manager (RM), b) from data packets(DP1, DP2) that have been transmitted or are to be transmitted over thetransmission path (US), the network transmission device (R1, R2) readsdata packet address information (A1, A2) identifying the origin anddestination of these data packets (DP1, DP2) and transmits thisinformation to the resource manager (RM), c) in order to establish aconnection of predetermined performance, a resource request (RA) withconnection information (A1, A2) identifying the origin and destinationof the connection is transmitted to the resource manager (RM), d) theresource manager (RM) uses the connection information (A1, A2) and thedata packet address information (A1, A2) to determine whether the originand destination of the connection match the origin and destination ofthe data packets (DP1, DP2), and if this is the case e) the availableset of resources on the transmission path (US) is taken intoconsideration in respect of the resource request for the furtherestablishment of the connection. 2) Method according to claim 1,characterized in that link information (LUS) for identifying thetransmission path (US) is transmitted to the resource manager (RM) withthe data packet address information (A1, A2). 3) Method according toclaims 1 and 2, characterized in that the establishment of a connectionis continued only if the resource request (RA) does not exceed theavailable set of resources on the transmission path (US). 4) Methodaccording to one of the preceding claims, characterized in that thenetwork transmission device (R1, R2) transmits resource information tothe resource manager (RM) concerning the available set of resources onthe transmission path (US). 5) Method according to one of the precedingclaims, characterized in that before transmitting the data packetaddress information (A1, A2), the network transmission device (R1, R2)checks whether identical data packet address information has alreadybeen sent earlier, and carries out the transmission only if this is notthe case. 6) Method according to one of the preceding claims,characterized in that depending on the data packet address information(A1, A2), the network transmission device (R1, R2) transmits routinginformation to the resource manager (RM) for recognizing connectionsrunning over the transmission path (US). 7) Method according to one ofthe preceding claims, characterized in that the transmission of the datapacket address information (A1, A2) of a data packet (DP1, DP2) to theresource manager (RM) is dependent on transmission information containedin the data packet (DP1, DP2) concerned. 8) Method according to one ofthe preceding claims, characterized in that the set of resources on thetransmission path (US) is managed by the resource manager (RM) accordingto service class and/or priority class. 9) Method according to one ofthe preceding claims, characterized in that the network transmissiondevice (R1, R2) is controlled by the resource manager (RM) in terms ofsafeguarding the performance of the connection. 10) Method according toone of the preceding claims, characterized in that a gatekeeper (GK) isprovided for the logical establishment of the connection.